The fertilization of animals by artificial insemination (AI) and embryo transplant following in vitro fertilization is an established practice. Because the viability and motility of the sperm used in these procedures affects the outcome of the procedures (i.e., whether the fertilization and insemination procedures successfully result in offspring), it is important that the sperm cells be able to survive the rigors often associated with the insemination process, including for example, the collection, storage, and transportation of the cells.
By way of example, in the livestock production industry, the ability to influence the reproductive outcome toward offspring having one or more preferred characteristics, such as offspring of a particular gender, is often desired. In order to effect such an outcome, semen samples from male mammals are collected, stained with a dye, subsequently sorted into X and Y chromosome-bearing cells, optionally stored for a period of time in a frozen or cooled state, and then transported to the location of breeding, where a female mammal is ultimately inseminated. Each of the steps of this process places a stress on the sperm cells that decreases sperm cell viability or motility, particularly progressive motility.
Salisbury et al. describe a technique for the collection of ejaculated bovine semen directly into a diluent which inhibits cell motility and prevents the absorption of carbohydrates from the surrounding seminal plasma. When the ejaculate is collected into the diluent and the air phase above the liquid is replaced by gassing with 100% CO2, the cells in the ejaculate became immotile. As long as the cells remained in the diluent and air was excluded, the cells remained immotile for several hours at room temperature and for at least 8 days at 5° C.